U.S. patent number 10,625,338 [Application Number 15/211,960] was granted by the patent office on 2020-04-21 for method for forming brace structures for additive manufacturing.
This patent grant is currently assigned to Applied Materials, Inc.. The grantee listed for this patent is Applied Materials, Inc.. Invention is credited to Bernard Frey, Ajey M. Joshi, Kasiraman Krishnan, Ashavani Kumar, Eric Ng, Hou T. Ng, Nag B. Patibandla, Bharath Swaminathan.
United States Patent |
10,625,338 |
Ng , et al. |
April 21, 2020 |
**Please see images for:
( Certificate of Correction ) ** |
Method for forming brace structures for additive manufacturing
Abstract
Additive manufacturing of an object includes dispensing a
plurality of successive layers of powder over a top surface of a
platform, fusing an object region in each of the plurality of
successive layers to form the object, and fusing a brace region in
a particular layer from the plurality of layers to form a brace
structure to inhibit lateral motion of the powder. The brace
structure is spaced apart from the particular object region by a
gap of unfused powder.
Inventors: |
Ng; Hou T. (Campbell, CA),
Patibandla; Nag B. (Pleasanton, CA), Joshi; Ajey M. (San
Jose, CA), Swaminathan; Bharath (San Jose, CA), Kumar;
Ashavani (Sunnyvale, CA), Ng; Eric (Mountain View,
CA), Frey; Bernard (Livermore, CA), Krishnan;
Kasiraman (Milpitas, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
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Assignee: |
Applied Materials, Inc. (Santa
Clara, CA)
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Family
ID: |
57775594 |
Appl.
No.: |
15/211,960 |
Filed: |
July 15, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170014907 A1 |
Jan 19, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62194159 |
Jul 17, 2015 |
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62361203 |
Jul 12, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C
64/40 (20170801); B22F 3/1055 (20130101); B29C
64/153 (20170801); C04B 35/653 (20130101); B33Y
10/00 (20141201); Y02P 10/295 (20151101); B22F
2003/1058 (20130101); C04B 2235/6026 (20130101); B33Y
30/00 (20141201); B29C 64/205 (20170801); Y02P
10/25 (20151101); B22F 2003/1056 (20130101) |
Current International
Class: |
C04B
35/65 (20060101); B29C 64/40 (20170101); B22F
3/105 (20060101); B29C 64/153 (20170101); C04B
35/653 (20060101); B33Y 10/00 (20150101); B33Y
30/00 (20150101); B29C 64/20 (20170101) |
Field of
Search: |
;419/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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104174846 |
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Dec 2014 |
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CN |
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2015-139957 |
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Aug 2015 |
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JP |
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WO 01-28733 |
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Apr 2001 |
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WO |
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WO 2014/124969 |
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Aug 2014 |
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WO |
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WO 2015-038072 |
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Mar 2015 |
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WO |
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WO 2015-108554 |
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Jul 2015 |
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WO |
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Other References
International Search Report and Written Opinion in International
Application No. PCT/US2016/052248, dated Dec. 21, 2016, 11 pages.
cited by applicant .
International Search report and Written Opinion in International
Application No. PCT/US2016/042598, dated Feb. 14, 2017, 13 pages.
cited by applicant .
Office Action in Chinese Application No. 201680054187.0, dated Jul.
25, 2019, 14 pages (with English translation). cited by
applicant.
|
Primary Examiner: Johnson; Edward M
Attorney, Agent or Firm: Fish & Richardson, P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Application
Ser. No. 62/194,159, filed on Jul. 17, 2015, and to U.S.
Provisional Application Ser. No. 62/361,203, filed on Jul. 12,
2016, the entirety of which are incorporated by reference.
Claims
What is claimed is:
1. A method for forming an object, the method comprising:
dispensing a plurality of successive layers of powder over a top
surface of a platform; fusing an object region in each of the
plurality of successive layers to form the object; and fusing a
brace region in a particular layer from the plurality of layers to
form a brace structure to inhibit lateral motion of the powder,
wherein the brace region is spaced apart from the particular object
region by a gap of unfused powder, and wherein the brace structure
of the particular layer comprises a plurality of strands extending
toward an outer perimeter of the particular layer.
2. The method of claim 1, wherein the brace region of the
particular layer extends from sufficiently near the particular
object region to inhibit relative motion between the object and the
unfused powder.
3. The method of claim 1, wherein forming the plurality of strands
comprises fusing a mesh region of the particular layer, the mesh
region defining a plurality of separated cells of unfused powder in
the particular layer.
4. The method of claim 3, wherein the plurality of separated cells
form a checkerboard pattern, a radial web pattern or a rectangular
pattern.
5. The method of claim 1, wherein: the particular layer is a first
particular layer of the plurality of successive layers, and the
method further comprises fusing a brace region in a second
particular layer of the plurality of successive layers, the brace
region of the second particular layer separated from a particular
object region of the second particular layer by a gap of unfused
powder, and the brace region of the second particular layer extends
toward an outer perimeter of the of the second particular
layer.
6. A method for forming an object, the method comprising:
dispensing a plurality of successive layers of powder over a top
surface of a platform, the plurality of successive layers of powder
comprising a first layer and a second layer; fusing an object
region in each of the plurality of successive layers to form the
object; and fusing a first brace region for the first layer to form
a first brace structure, wherein the first brace region is spaced
apart from a particular object region by a gap of unfused powder,
and wherein the brace region of the first layer surrounds a first
object region of the first layer.
7. The method of claim 6, further comprising fusing a second brace
region for the second layer to form a second brace structure,
wherein the second brace region of the second layer surrounds a
second object region of the second layer and is spaced apart from
the second object region by a second gap of unfused powder.
8. The method of claim 7, wherein fusing the second brace region
comprises fusing the second brace region in the second layer such
that the brace structure comprises a vertical brace member
extending vertically through the second layer, the vertical brace
member connecting the second brace structure to the first brace
structure.
9. The method of claim 8, further comprising fusing a brace region
in each of the plurality of successive layers to form a brace
structure in each of the plurality of successive layers, wherein
fusing the brace region in each of the plurality of successive
layers comprises fusing the first brace region and fusing the
second brace region.
10. The method of claim 7, further comprising, before fusing the
first brace region and the second region: computing a geometric
overlap between a first portion of the object corresponding to the
first object region and a second portion of the object
corresponding to the second object region, and determining the
geometric overlap is less than a threshold overlap.
11. A method for forming an object, the method comprising:
dispensing a plurality of successive layers of powder over a top
surface of a platform, the plurality of successive layers of powder
comprising a first layer and a second layer; fusing an object
region in each of the plurality of successive layers to form the
object; and fusing a first brace region for the first layer to form
a first brace structure, wherein the brace region is spaced apart
from a particular object region by a gap of unfused powder, and
wherein the brace structure includes a brace member and a keyed
portion along the brace member, the keyed portion having a
thickness greater than a thickness of the brace member.
12. The method of claim 11, wherein the first layer is an uppermost
layer of the plurality of successive layers.
13. The method of claim 11, further comprising after fusing the
object region and fusing the brace region, removing the brace
structure and the object from the platform, and removing the brace
structure from the object by controlling an end effector having a
lock portion engageable with the keyed portion.
14. The method of claim 11, wherein removing the brace structure
from the object comprises sliding the brace structure relative to
the object.
Description
TECHNICAL FIELD
This specification relates to additive manufacturing, also known as
3D printing.
BACKGROUND
Additive manufacturing (AM), also known as solid freeform
fabrication or 3D printing, refers to a manufacturing process where
three-dimensional objects are built up from successive dispensing
of raw material (e.g., powders, liquids, suspensions, or molten
solids) in two-dimensional layers. In contrast, traditional
machining techniques involve subtractive processes in which objects
are cut out from a stock material (e.g., a block of wood, plastic
or metal).
A variety of additive processes can be used in additive
manufacturing. Some methods melt or soften material to produce
layers, e.g., selective laser melting (SLM) or direct metal laser
sintering (DMLS), selective laser sintering (SLS), fused deposition
modeling (FDM), while others cure liquid materials using different
technologies, e.g., stereolithography (SLA). These processes can
differ in the way layers are formed to create the finished objects
and in the materials that are compatible for use in the
processes.
Conventional systems use an energy source for sintering or melting
a powdered material. Once all the selected locations on the first
layer are sintered or melted and then re-solidified, a new layer of
powdered material is deposited on top of the completed layer, and
the process is repeated layer by layer until the desired object is
produced.
SUMMARY
In one aspect, a method for forming an object includes dispensing a
plurality of successive layers of powder over a top surface of a
platform, fusing an object region in each of the plurality of
successive layers to form the object, and fusing a brace region in
a particular layer from the plurality of layers to form a brace
structure to inhibit lateral motion of the powder. The brace region
is spaced apart from the particular object region by a gap of
unfused powder. The brace structure of the particular layer
includes a plurality of strands extending toward an outer perimeter
of the particular layer.
In another aspect, a method for forming an object includes
dispensing a plurality of successive layers of powder over a top
surface of a platform, the plurality of successive layers of powder
comprising a first layer and a second layer, fusing an object
region in each of the plurality of successive layers to form the
object, and fusing a first brace region for the first layer to form
a first brace structure. The brace region is spaced apart from the
particular object region by a gap of unfused powder. The brace
region of the first layer surrounds a first object region of the
first layer.
In another aspect, a method for forming an object includes
dispensing a plurality of successive layers of powder over a top
surface of a platform, fusing an object region in each of the
plurality of successive layers to form the object, and fusing a
brace region of at least one layer to form a first brace structure.
The brace region is spaced apart from the particular object region
by a gap of unfused powder. The brace structure includes a brace
member and a keyed portion along the brace member, the keyed
portion having a thickness greater than a thickness of the brace
member.
Implementations of any aspect may include one or more of the
following features.
The brace region of the particular layer may at least partially
surround, e.g., entirely surround, a particular object region of
the particular layer.
The brace structure of the particular layer may include a plurality
of strands extending toward an outer perimeter the particular
layer. The brace region may extend from sufficiently near the
particular object region to inhibit relative motion between the
object and the unfused powder.
Fusing the brace region may include fusing the brace region to form
a brace member of the brace structure and to form a keyed portion
along the brace member, the keyed portion having a thickness
greater than a thickness of the brace member. The particular layer
may be an uppermost layer of the plurality of successive layers.
After fusing the object region and fusing the brace region, the
brace structure and the object may be removed from the platform.
The brace structure may be removed from the object by controlling
an end effector having a lock portion engageable with the keyed
portion. Removing the brace structure from the object may include
sliding the brace structure relative to the object.
Fusing the brace region may include fusing an object perimeter
region for the particular layer to form a perimeter brace spaced
apart from and surrounding a perimeter of the particular object
region. An offset distance may be determined based on the perimeter
of the particular object region. Fusing the object perimeter region
may include fusing the object perimeter region such that the
perimeter brace is offset from the perimeter of the particular
object region by the offset distance. Determining the offset
distance may include determining the offset distance based on a
perimeter of the object region in each of the plurality of
successive layers. Determining the offset distance may include
determining the offset distance such that the perimeter of the
object perimeter region, as projected on the top surface, contains
at least one of the perimeter of the object region of each of the
plurality of successive layers beneath the particular layer, as
projected on the top surface, or the perimeter of the object region
of each of the plurality of successive layers above the particular
layer, as projected on the top surface. The offset distance may be
between one and ten voxels.
Fusing the brace region for the particular layer may include fusing
an object perimeter region to form a perimeter brace spaced apart
from and surrounding a perimeter of the particular object region,
and forming a plurality of strands extending from the perimeter
brace toward the outer perimeter of the platform. Forming the
plurality of strands may include fusing a mesh region of the
particular layer. The plurality of strands may define a plurality
of separated cells of unfused powder in the particular layer. The
plurality of separated cells form a checkerboard pattern, a radial
web pattern or a rectangular pattern.
The particular layer may be a first particular layer of the
plurality of successive layers. A brace region may be fused in a
second particular layer of the plurality of successive layers. The
brace region of the second particular layer may at least partially
surrounding a particular object region of the second particular
layer by a gap of unfused powder. The brace region of the second
particular layer may extend toward an outer perimeter of the second
particular layer.
A bottommost layer of powder may be dispensed beneath the plurality
of successive layers and the platform. Fusing the object region may
include fusing the object region while the bottommost layer of
powder is unfused powder. An outer perimeter of the brace region
may be inwardly offset from the outer perimeter of the
platform.
Fusing the second brace region may include fusing the second brace
region in the second layer such that the brace structure comprises
a vertical brace member extending vertically through the second
layer, the vertical brace member connecting the second brace
structure to the first brace structure. A brace region may be fused
in each of the plurality of successive layers to form a brace
structure in each of the plurality of successive layers. Fusing the
brace region in each of the plurality of successive layers may
include fusing the first brace region and fusing the second brace
region. After fusing the object region in each of the plurality of
successive layers and fusing the first brace region and the second
brace region, the first brace structure may be removed from the
object by moving first brace structure in a first direction
relative to the object, and the second brace structure from the
object may be removed by moving the second brace structure in a
second direction relative to the object, the second direction being
opposite the first direction. Before fusing the first brace region
and the second region, a geometric overlap between a first portion
of the object corresponding to the first object region and a second
portion of the object corresponding to the second object region may
be computed. The geometric overlap may be determined to be less
than a threshold overlap. The threshold overlap may be a threshold
percent overlap between 50% and 90%.
In another aspect, an additive manufacturing apparatus for forming
a part includes a support, a dispenser to deliver a plurality of
successive layer of powder on the support, an energy source to fuse
selected portions of an outermost layer of powder, and a controller
coupled to the energy source. The controller is configured to cause
the energy source to fuse an object region in each of the plurality
of successive layers to form the object, and fuse a brace region in
a particular layer from the plurality of layers to form a brace
structure to inhibit lateral motion of the powder. The brace region
of the particular layer is spaced apart from the particular object
region by a gap of unfused powder, and at least one of i) the brace
region comprises a plurality of strands extending toward an outer
perimeter of the particular layer, ii) the brace region surrounds
an object region of the first layer, or iii) the brace structure
includes a brace member and a keyed portion along the brace member,
the keyed portion having a thickness greater than a thickness of
the brace member.
Implementations may include one or more of the following
features.
The controller may be configured to cause the energy source to fuse
the brace structure of the particular layer to include a plurality
of strands extending toward an outer perimeter of the of the
particular layer. The controller may be configured to cause the
energy source to fuse the brace region to form a brace member of
the brace structure and to form a keyed portion along the brace
member. The keyed portion may hayed a thickness greater than a
thickness of the brace member. The particular layer may be an
uppermost layer of the plurality of successive layers.
The controller may be configured to control the energy source to
fuse an object perimeter region for the particular layer to form a
perimeter brace spaced apart from and surrounding a perimeter of
the particular object region. The controller is configured to
determine an offset distance based on the perimeter of the
particular object region, and to cause the energy source to fuse
the object perimeter region such that the perimeter brace is offset
from the perimeter of the particular object region by the offset
distance. The controller may be configured to determine the offset
distance based on the perimeter of the particular object region by
determining the offset distance based on a perimeter of the object
region in each of the plurality of successive layers. The
controller is configured to determine at least one of the perimeter
of the object region of each of the plurality of successive layers
beneath the particular layer, as projected on the top surface, or
the perimeter of the object region of each of the plurality of
successive layers above the particular layer, as projected on the
top surface. The offset distance is between one and ten voxels.
The controller may be configured to cause the energy source to fuse
an object perimeter region to form a perimeter brace spaced apart
from and surrounding a perimeter of the particular object region,
and form a plurality of strands extending from the perimeter brace
toward the outer perimeter of the platform. The plurality of
strands may form a mesh region of the particular layer. The
plurality of strands may define a plurality of separated cells of
unfused powder in the particular layer. The plurality of separated
cells form a checkerboard pattern, a radial web pattern, or a
rectangular pattern.
Advantages of the foregoing may include, but are not limited to,
the following. The brace structures can inhibit relative movement
between the object and unfused powder, enabling greater achievable
resolutions for the object. The brace structures can also reduce
manufacturing defects that may occur during a build process due to
shifting of the unfused powder during, for example, movement of the
build platform. The brace structures, by being separated from the
build platform and the side walls extending from the build
platform, do not fuse to the build platform and the side walls. In
this regard, the process of building and removing the brace
structures can result in a reduced amount of residual fused or
semi-fused powder on the build platform or the side walls after the
object and the brace structures are removed. In examples where the
brace structures are built to be separated from the object by a
gap, the process of removing the brace structures from the
workpiece may result in fewer manufacturing defects. In particular,
because the removal process does not necessitate an operation of
breaking a connection between a supporting structure, e.g., the
brace structure, and the workpiece.
The details of one or more implementations of the subject matter
described in this specification are set forth in the accompanying
drawings and the description below. Other potential features,
aspects, and advantages will become apparent from the description,
the drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a schematic side view of an example of an additive
manufacturing apparatus.
FIG. 1B is a schematic top view of the additive manufacturing
apparatus of FIG. 1A.
FIG. 2 is a schematic front perspective view of an object and a
brace structure.
FIG. 3A is a top horizontal cross-sectional view of an additive
manufacturing apparatus having formed an example of an object and a
brace structure.
FIG. 3B is a top horizontal cross-sectional view of an additive
manufacturing apparatus having formed another example of an object
and a brace structure.
FIG. 3C is a top horizontal cross-sectional view of an additive
manufacturing apparatus having formed yet another example of an
object and a brace structure
FIGS. 4A to 4F are each a side vertical cross-sectional view of an
additive manufacturing apparatus performing an operation to form an
object.
FIG. 5 is a side vertical cross-sectional view of an additive
manufacturing apparatus having formed an example of an object and a
brace structure.
FIG. 6 is a side vertical cross-sectional view of an additive
manufacturing apparatus having formed another example of an object
and a brace structure formed by.
Like reference numbers and designations in the various drawings
indicate like elements.
DETAILED DESCRIPTION
Additive manufacturing (AM) apparatuses can form an object by
dispensing and fusing successive layers of a powder on a build
platform. As the apparatus forms the object on the build platform,
the powder and the object need to be supported on the build
platform. Although the powder can be restrained by a side wall, the
powder may shift during operation, resulting in distortion of the
object being constructed. For example, this shifting might occur if
the build platform is significantly larger than the object.
However, a structure can be fabricated on the build platform to
inhibit shifting between the object and the powder. For some or
each of the layers, the apparatus fuses a portion of the powder
that becomes a structure to support the object and the unfused
powder. This structure, e.g., a brace structure, supports the
object by inhibiting relative motion between the object and unfused
powder within the successive layers dispensed on the build
platform.
The brace structure, in some implementations, supports the object
without being fused to the object, without being fused to the build
platform, and/or without being fused to side walls extending
vertically from the build platform. In this regard, in some
examples, the brace structure is spaced apart from the object, the
build platform, and/or the side walls. The brace structure extends
through each layer or can extend through a subset of the successive
layers dispensed. The brace structure extends from near the object
outwardly toward a perimeter of the build platform and/or a
perimeter of the layer of the powder. The brace structure, for
example, includes a perimeter brace surrounding the object. Several
strands extend horizontally above the build platform from the
perimeter brace toward an outer perimeter of the build platform. In
some cases, strands extending horizontally are connected by strands
extending vertically above the build platform. Near an outer
perimeter of the build platform, the brace structure includes an
outer perimeter brace that is spaced apart from the outer perimeter
of the build platform so that the brace structure does not contact
the side walls. Optionally, the brace structure forms a cell or
mesh structure extending from near the object to the perimeter of
the build platform. For example, the strands may be cross-linked to
form a mesh pattern.
Additive Manufacturing Apparatuses
FIGS. 1A and 1B show a schematic side view and top view,
respectively, of an example additive manufacturing (AM) apparatus
100 that executes additive manufacturing operations to form an
object and a brace structure to support the object. The apparatus
100 includes a build platform 104, a first dispensing system 122 to
deliver layers of powder to the build platform 104, and an energy
source 124 to fuse selected regions of the powder on the build
platform 104.
Optionally, the first dispensing system 122 and/or the energy
source 124 can be incorporated into a printhead 102 that is
movable, e.g., vertically and/or horizontally, relative to the
build platform 104. For example, referring to FIGS. 1A and 1B, the
printhead 102 is supported on a gantry 110 configured to traverse
the build platform 104. The gantry 110 includes, in some cases, a
horizontally extending support on which the printhead 102 is
mounted. The gantry 110 can be driven along rails 112 by a linear
actuator and/or motor so as to move across the build platform 104
along a first axis parallel to a forward direction 114.
Alternatively, the first dispensing system 122 and/or the energy
source 124 can be mounted on the build platform 104, or be mounted
separately, e.g., on a frame supporting the build platform 104 or
on chamber wall that surrounds the build platform 104.
The build platform 104 can be moved upward or downward during build
operations. For example, the build platform 104 can be moved
downward with each layer dispensed by the first dispensing system
122 so that the dispensing system 122 and energy source 124 remain
at the same vertical height relative to the outermost layer of
powder.
The first dispensing system 124 can include a roller that is
positioned above the platform and which has apertures through which
the powder passes. Alternatively, the first dispensing system 124
can include a powder delivery bed positioned adjacent the build
platform, and a powder pusher, e.g. a blade or a roller, that moves
laterally to push powder particles from the powder delivery bed
over the build platform. Alternatively, the first dispensing system
can include a powder ejection system. For example, the first
dispensing system can include one or more nozzles that eject the
powder particle. Such a dispending system can deliver the powder
particles in a carrier liquid, e.g. a high vapor pressure carrier,
to form the layers of powder material. The carrier fluid can
evaporate prior to the sintering step for the layer, e.g., prior to
the second particles being dispensed. Alternatively, a dry
dispensing mechanism, e.g., one or more nozzles assisted by
ultrasonic agitation and pressurized inert gas, can be employed to
dispense the powder.
In some implementations, the energy source 124 can include a
scanning laser that generates a beam of focused energy that
increases a temperature of a small area of the layer of the powder.
The energy source 124 can fuse the powder by using, for example, a
sintering process, a melting process, or other process to cause the
powder to form a solid mass of material.
In some cases, the energy source 124 can include an ion beam or an
electron beam.
The energy source 124 can be positioned on the printhead 102 such
that, as the printhead 102 advances in the forward direction 114,
the energy source 124 can cover lines of powder dispensed by the
dispensing system 122. When the apparatus 100 includes multiple
dispensing systems, the printhead 102 can also optionally include
an energy source for each of the dispensing systems.
Optionally, the apparatus 100 includes a heat source 126 to direct
heat to raise the temperature of the deposited powder. The heat
source 126 can heat the deposited powder to a temperature that is
below its sintering or melting temperature. The heat source 126 can
be, for example, a heat lamp array. The lamp array can
simultaneously heat the entire layer of the powder. The heat source
126 can be incorporated into the printhead 102, mounted on the
build platform 104, or be mounted separately, e.g., on a frame
supporting the build platform 104 or on chamber wall that surrounds
the build platform 104. The heat source 126 can be located,
relative to the forward moving direction 114 of the printhead 102,
behind the first dispensing system 122. As the printhead 102 moves
in the forward direction 114, the heat source 126 moves across the
area where the first dispensing system 122 was previously located
to provide heat to the powder 106 most recently dispensed by the
first dispensing system 122.
In some implementations, the heat source 126 is a digitally
addressable heat source in the form of an array of individually
controllable light sources. The array includes, for example,
vertical-cavity surface-emitting laser (VCSEL) chips, positioned
above the build platform 104. The array of controllable light
sources can be a linear array driven by an actuator of a drive
system to scan across the build platform 104. In some cases, the
array is a full two-dimensional array that selectively heats
regions of the layer by activating a subset of the individually
controllable light sources.
In some implementations, the build platform 104 may include a
heater that can heat powder dispensed on the build platform 104.
The heater can be an alternative to or in addition to the heat
source 126 of the printhead 102.
Optionally, the apparatus 100 can also include a first spreader
128, e.g., a roller or blade, that cooperates with first the
dispensing system 122 to compact and spread powder dispensed by the
dispensing system 122. The spreader 128 can provide the layer with
a substantially uniform thickness. In some cases, the first
spreader 128 can press on the layer of powder to compact the
powder. The spreader 128 can be supported by the printhead 102, or
separately.
The apparatus 100 also, optionally, includes a first sensing system
130 and/or a second sensing system 132 to detect properties, e.g.,
temperature, density, and material, of the apparatus 100 as well as
powder dispensed by the dispensing system 122.
In some implementations, the apparatus 100 includes a second
dispensing system 136 to dispense the second powder 108. The second
dispensing system 136 can use any of the dispensing techniques
discussed above for the first dispensing system. A second spreader
134 can operate with the second dispensing system 136 to spread and
compact the second powder 108. The apparatus 100 can also include a
second heat source that, like the first heat source 126, directs
heat to powder in large areas of the build platform 104. If the
apparatus 100 includes multiple heat sources and multiple energy
sources on the printhead 102, each of the energy sources can be
located immediately ahead of one of the heat sources (for the usual
direction of motion when dispensing powder).
If present, the second dispensing system 136 enables delivery a
second type of powder 108 having properties that differ from those
of the first powder 106. The first powder particles 106 can have a
larger mean diameter than the second particle particles 108, e.g.,
by a factor of two or more. When the second powder particles 108
are dispensed on a layer of the first powder particles 106, the
second powder particles 108 infiltrate the layer of first powder
particles 106 to fill voids between the first powder particles 106.
The second powder particles 108, being smaller than the first
powder particles 106, can achieve a higher resolution.
Alternatively or in addition, if the apparatus 100 includes two
types of powders, the first powder particles 106 can have a
different sintering temperature than the second particle particles.
For example, the first powder can have a lower sintering
temperature than the second powder. In such implementations, the
energy source 124 can be used to heat the entire layer of powder to
a temperature such that the first particles fuse but the second
powder does not fuse.
In some implementations, the controller 138 can control the first
and second dispensing systems 122, 136 to selectively deliver the
first and the second powder particles 106, 108 to different
regions. In implementations when multiples types of powders are
used, the first and second dispensing systems 122, 136 can deliver
the first and the second powder particles 106, 108 each into
selected areas, depending on the resolution requirement of the
portion of the object to be formed or the portion of the brace
structure to be formed.
Materials for the powder include metals, such as, for example,
steel, aluminum, cobalt, chrome, and titanium, alloy mixtures,
ceramics, composites, and green sand. In implementations with two
different types of powders, in some cases, the first and second
powder particles 106, 108 can be formed of different materials,
while, in other cases, the first and second powder particles 106,
108 have the same material composition. In an example in which the
apparatus 100 is operated to form a metal object and dispenses two
types of powder, the first and second powder particles 106, 108 can
have compositions that combine to form a metal alloy or
intermetallic material.
A controller 138 can coordinate the operations of the energy source
124 and the first dispensing system 122. The controller 138 also
coordinates the operations of, if present, the heat source 126, the
spreaders 128, 134, the first and second sensing systems 130, 132,
and the second dispensing system 136. The controller 138 can also
receive signals from, for example, user input on a user interface
of the apparatus or sensing signals from sensors of the apparatus
100.
The controller 138 can operate the first dispensing system 122 to
control, for example, the thickness and the distribution of the
powder 106 dispensed on the build platform 104. The thickness of
each layer depends on, for example, the number of the powder
particles 106 stacked through a height of the layer or the mean
diameter of the powder particles 106. In some implementations, each
layer of the powder particles 106 is a single particle thick. In
some cases, each layer has a thickness resulting from stacking
multiple powder particles 106 on top of each other.
To move the build platform 104 up and down during build operations,
the controller 138 can operate a drive mechanism, e.g., a piston or
linear actuator, connected to the build platform 104 to decrease a
height of the build platform 104 so that the build platform 104 can
be moved away from the printhead 102. Alternatively, the build
platform 104 can be held in a fixed vertical position, and the
gantry 110 can be raised after each layer is deposited.
The controller 138 can include a computer aided design (CAD) system
that receives and/or generates CAD data. The CAD data is indicative
of the object to be formed, and, as described herein, can be used
to determine properties of the structures formed during additive
manufacturing processes. Based on the CAD data, the controller 138
can generate instructions usable by each of the systems operable
with the controller 138, for example, to dispense the powder 106,
to fuse the powder 106, to move various systems of the apparatus
100, and to sense properties of the systems, powder, and/or the
object.
The controller 138, for example, can transmit control signals to
drive mechanisms that move various components of the apparatus. In
some implementations, the drive mechanisms can cause translation
and/or rotation of these different systems, including dispensers,
rollers, support plates, energy sources, heat sources, sensing
systems, sensors, dispenser assemblies, dispensers, and other
components of the apparatus 100. Each of the drive mechanisms can
include one or more actuators, linkages, and other mechanical or
electromechanical parts to enable movement of the components of the
apparatus.
The controller 138, in some cases, controls movement of the
printhead 102 and can also control movements of individual systems
of the printhead 102. For example, the controller 138 can cause the
printhead 102 to move to a particular location along the gantry
110, and the controller 138 can transmit a separate control signal
to drive a separate drive mechanism to move the energy source 124
of the printhead 102 along the printhead 102. The apparatus 100 can
further include a drive mechanism that moves the gantry 110 along
the build platform 104 so that the printhead 102 can be positioned
above different areas of the build platform 104.
During build operations, the controller 138 controls the dispensing
system 122 to dispense the powder 106. The controller 138 can
operate the dispensing system 122 to dispense successive layers
140a-140e of the powder 106.
The controller 138 can also operate the energy source 124 and, if
present, the heat source 126 to fuse portions of each of the
successive layers 140a-140e of the powder 106 to form a workpiece
142 that becomes the object to be formed. The workpiece 142 formed
by the energy source 124 extends through several layers, e.g., the
layers 140b-140e.
Brace Structures
The controller 138 controls the energy source 124 to fuse the
powder 106 to form a brace structure 144. The brace structure 144
extends through the unfused powder 106 surrounding the workpiece
142 and can function as structural support that limits relative
movement and shifting between the workpiece 142 and the unfused
powder 106 as subsequent layers are dispensed and fused on top of
the layers 140a-140e. The brace structure 144 therefore is a fused
structure that does not form the object to be built by the
apparatus 100.
In some implementations, after the dispensing system 122 dispenses
the first layer 140a, the controller 138 proceeds to control the
dispensing system 122 to dispense the second layer 140b on top of
the first layer 140a without fusing any of the powder 106 within
the first layer 140a. The first layer 140a corresponds to the
bottommost layer of the successive layers dispensed by the
dispensing system 122 and thus is beneath the layers 140b-140e. The
controller 138 controls the energy source 124 to fuse portions of
the powder 106 within the layers 140b-140e--dispensed on top of the
first layer 140a and the build platform 104--to form the workpiece
142. The controller 138 also controls the energy source 124 to fuse
portions of the powder 106 in the layers 140a to 140e to form the
brace structure 144. The first layer 140a of the unfused powder can
inhibit adhesion between fused powder and the build platform
104.
The controller 138 can control the energy source 124 to fuse a
portion of the powder 106 within a single layer to form
horizontally extending strands of the brace structure 144. The
energy source 124 fuses the powder 106 within, for example, the
second layer 140b to form strands 144a, 144b that extend
horizontally above the build platform 104 and through the second
layer 140b.
In some examples, the strands 144a, 144b do not contact the
workpiece 142. The strands 144a, 144b are separated from the
portion of the workpiece 142 within the layer 140b by a gap 145.
The gap 145 is, for example, filled with unfused powder 106.
Optionally, the strands 144a, 144b do not contact side walls of the
apparatus 100, e.g., side walls that extend upwardly from the build
platform 104 to contain the powder 106 within a confined area above
the build platform 104.
The strands 144a, 144b extend horizontally and therefore can be
formed from powder 106 within a single layer, e.g., the layer 140b.
In some cases, the horizontally extending strands 144a, 144b can be
formed of powder 106 within two or more layers to form thicker
strands.
In some examples, the controller 138 can control the energy source
124 to fuse horizontally extending strands in multiple layers. The
energy source 124 fuses the powder 106 within, for example, the
fifth layer 140e to form a strand 144c of the brace structure 144
that extends horizontally above the build platform 104 and through
the fifth layer 140e.
FIG. 1A depicts the apparatus 100 during the fusing operation for
the layer 140e. In this regard, the strand 144c is not necessarily
completely formed. In some examples, similar to the strands 144a,
144b, the strand 144c is formed such that the strand 144c does not
contact the workpiece 142, particular the portion of the workpiece
142 to be formed in the fifth layer 140e.
In some cases, the controllers 138 controls the energy source 124
to fuse the powder 106 within a portion through several layers. The
energy source 124 fuses the powder 106 within, for example, the
layers 140c-140d to form a vertically extending strand 144d, shown
in FIG. 1A, of the brace structure 144 that connects the
horizontally extending strands 144b and 144c. The vertically
extending strand 144d can inhibit relative horizontal motion
between the strands 144b and 144c.
Each of the strands 144a, 144b, 144c, 144d shown in FIG. 1A and
described above is described in greater detail with respect to FIG.
2, which shows the workpiece 142 supported by the brace structure
144 on top of the build platform 104. The strands 144a, 144b extend
from near the workpiece 142 outwardly toward an outer perimeter
104a of the build platform 104. Within the layer forming the
strands 144a, 144b, the brace structure 144 includes several
strands 146--including the strands 144a, 144b--that radiate from
the near the workpiece 142 toward the outer perimeter 104a of the
build platform 104. In some implementations, the strands 146 extend
radially relative to an area centroid 147 of a horizontal
cross-section of the workpiece 142. Alternatively, the strands 146
extend outward from the workpiece 142 but do not extend radially
relative to the area centroid.
The strands 146 can be connected by one or more connecting strands
148a, 148b, 148c (collectively referred to as connecting strands
148) that extend in a direction non-parallel to, e.g.,
perpendicular to, at an angle to, and/or away from, the strands
146. The connecting strands 148 inhibit relative motion between the
strands 146. The connecting strands 148 also provide structural
strength for the brace structure 144 to inhibit deflection of the
strands 146.
Within the layer or layers of powder 106 where they are formed, the
strands 146 and the strands 148 cooperate to define separated cells
149. The cells 149, during the build operations, contain unfused
powder that separate adjacent strands 146 and that separate, if
present, adjacent strands 148. As shown in FIG. 2, each of the
cells 149 has edges that are defined by the strands 146 and edges
that are defined by the strands 148. In implementations where the
strands 146 extend radially outwardly relative to the workpiece 142
or relative to the area centroid of the cross-section of the
workpiece 142 within the layers where the strands 146 are formed,
the strands 146 and the strands 148 cooperate to form a radial web
pattern of the cells 149.
The connecting strand 148 can include strands positioned near the
workpiece 142. The strands can form a perimeter brace surrounding
the workpiece 142 or adjacent to the workpiece 142. In some
examples, the connecting strands 148 of the brace structure 144
include an inner perimeter strand 148a that surrounds the portion
of the workpiece 142 in the layer that forms the strands 146. The
inner perimeter strand 148a of the brace structure 144 is
positioned near the workpiece 142 but is separated from the
workpiece 142 by the gap 145. In some implementations, the inner
perimeter strand 148a partially surrounds the workpiece 142.
The gap 145 between the inner perimeter strand 148a and the
workpiece 142 is sized and dimensioned to inhibit relative motion
between the workpiece 142 and the unfused powder. In some examples,
the gap 145 has a size between 1 and 10 voxels, e.g., the
dispensing system 122 can dispense 1 to 10 voxels of the powder 106
within the gap 145. In some implementations, the gap 145 is uniform
has a uniform size around the workpiece 142 such that the gap 145
has a shape corresponding to an outermost perimeter of the
workpiece 142.
In some implementations, this outermost perimeter can be the outer
perimeter of the 2-D shape that occurs if the 3-D workpiece is
projected onto the plane of the build platform 104, which can be
computed by the controller 138. The inner perimeter strand 148a
therefore can form a vertical wall that is uniformly spaced from
the outermost perimeter of the workpiece 142 by an offset distance,
where the offset distance is, for example, 1 to 10 voxels. The
inner perimeter strand 148a can be a closed loop.
In some implementations, this outermost perimeter is the outer
perimeter of the 3-D workpiece. In this case, the inner perimeter
strand 148a is uniformly spaced from the outermost perimeter of the
workpiece 142 by an offset distance, but mimics the curvature of
the workpiece along the vertical axis.
The strands 146, extending away from near the workpiece 142, can
terminate at an outer perimeter strand 148b positioned near the
outer perimeter 104a of the build platform 104. The outer perimeter
strand 148b can be formed to match the shape of the outer perimeter
104a of the build platform 104. In particular, the outer perimeter
strand 148b can follow the outer perimeter 104a of the build
platform 104 without crossing the outer perimeter 104a or without
contacting, if present, the side walls of the build platform 104
that define the outer perimeter 148b of the build platform 104.
In some examples, the outer perimeter strand 148b is inwardly
offset from the outer perimeter 104a of the build platform 104. The
outer perimeter strand 148b can be inwardly offset by an offset
distance. The offset distance can be between 1 and 10 voxels.
Optionally, the outer perimeter strand 148b is a closed loop.
The inner perimeter strand 148a and the outer perimeter strand
148b, in combination with the unfused powder, support the workpiece
142 above the build platform 104 without direct contact between the
brace structure 144 and the workpiece 142, the brace structure and
build platform 104, and/or the brace structure 144 and the side
walls. The absence of contact can reduce residual fused material on
the workpiece 142, the build platform 104, and the side walls after
the brace structure 144 is removed.
The brace structure 144 can additionally or alternatively include
one or more interior connecting strands 148c positioned along the
strands 146 between the starting point of the strands 146 near the
workpiece 142 and the ending point of the strands 146 near the
outer perimeter 104a of the build platform 104. The interior
connecting strand 148c is positioned between, if present, the outer
perimeter strand 148b and the inner perimeter strand 148a. Each of
the interior connecting strands 148c can be closed loops.
FIG. 2 shows a first level 150a and a second level 150b of the
brace structure 144. The first level 150a of the brace structure
144 includes the strands 146 and the strands 148 described herein.
The second level 150b can include radiating strands, e.g., similar
to the strands 146, and connecting strands, e.g., similar to the
strands 148. FIG. 2 depicts, for example, a portion of the brace
structure 144 of FIG. 1A including the horizontally extending
strand 144c as well as the portion of workpiece 142 in the same
layer as the horizontally extending strand 144c complete. The
horizontally extending strand 144c, like the strands 144a, 144b,
extend toward the outer perimeter 104a of the build platform
104.
The brace structure 144 can include several strands 152, including
the strand 144d that extend vertically between the first level 150a
and the second level 150b of the brace structure 144. In some
examples, the strands 152 connect to the first level 150a where one
of the strands 148 connects with one of the strands 146.
The geometry of the brace structure can vary depending on the
geometry of the object to be formed. FIG. 3A shows a horizontal
cross-section of a workpiece 154 having an amorphous geometry. A
brace structure 156 supporting the workpiece 154 can have a
geometry that matches the contours of the horizontal cross-section
of the workpiece 154. In this regard, a gap 158 defined between an
inner perimeter strand 160 of the brace structure 156 and the
workpiece 154 can have a uniform offset such that the inner
perimeter strand 160 has a similar geometry as the horizontal
cross-section of the workpiece 154. Optionally, interior connecting
strands 162 also have geometries similar to the geometry of the
horizontal cross-section. For example, the interior connecting
strands 162 has a shape having a perimeter that is a scaled
representation of the perimeter of the horizontal cross-section of
the workpiece 154.
In some examples, to facilitate removal of a brace structure from
the build platform of the apparatus, the brace structure includes
enlarged fused portions. A robot arm controllable by the controller
of the apparatus is able to grasp onto the enlarged fused portions
of the brace structure and carry the brace structure from the build
platform. As shown in FIG. 3B, depicting a horizontal cross-section
of a brace structure 164 supporting a workpiece 166, the brace
structure 164 includes keyed portions 168 along one or more of the
horizontally extending strands forming the brace structure 164. The
keyed portions 168 are positioned, for example, along an inner
perimeter strand of the brace structure 164. In some
implementations, the keyed portions 168 are positioned on interior
connecting strands or on other horizontally extending strands. The
keyed portions 168 additionally or alternatively are positioned
along vertically extending strands.
The geometry of the keyed portions 168 enables the robot arm to
easily grasp the brace structure 164. In some examples, the keyed
portions 168 are solid fused structures with a greater thickness
than the strands of the brace structure 164. In some examples, the
keyed portions 168 are formed from several interconnected strands
having a thickness equal to the thickness of the other strands of
the brace structure 164. The strands of the keyed portions 168 are,
for example, closely spaced to form a structure that the robot arm
can grasp. These strands can form a truss structure with sufficient
structural strength to support the weight of the brace structure
164 when the keyed portions 168 are grasped by the robot arm.
Optionally, to facilitate access by the robot arm of the apparatus,
the keyed portions 168 are positioned on outer levels of the brace
structure 164. For example, the keyed portions 168 can be
positioned on an uppermost level of the brace structure 164 so that
the robot arm can grasp the brace structure 164 from above the
build platform 104. The keyed portions 168, alternatively or
additionally, are formed along a lowermost level of the brace
structure 164. If the keyed portions 168 are positioned on the
lowermost level, the brace structure 164 can be removed from the
build platform with the workpiece 166. The brace structure 164 can
then be removed from a lower end of the workpiece 166.
For each level of the brace structure, the horizontally extending
strands can be configured to form various geometries depending on
the geometry of the workpiece. When the controller receives the CAD
data for an object to be formed, the controller can determine
configurations of the horizontally extending strands so that the
brace structure provides greater support for the workpiece in some
areas while providing less support in other areas. In particular,
the portions of the object with geometries that may require greater
resolution to achieve the geometry specified in the CAD data may
benefit from greater support from the brace structure to achieve
that greater resolution.
For example, if a portion of the object has a smaller radius of
curvature, the controller can control the energy source such that
the brace structure within the region surrounding that portion of
the object has a greater density of strands, e.g., a greater number
of strands per unit area. The brace structure can accordingly
better inhibit movement of the surrounding unfused powder within
that area. As a result, the energy source can achieve the higher
resolution that may be necessary for the lower radius of curvature
of the portion of the object.
In one example, as shown in FIG. 3C, a workpiece 170 having a
horizontal cross-section with amorphous geometry is supported by a
brace structure 172. The workpiece 170 includes a curved portions
172a, 172b, 172c. The curved portions 172a and 172b have radii of
curvatures smaller than a radius of curvature of the curved portion
172c.
Because of the smaller radii of curvatures of the curved portions
172a, 172b, the brace structure 172 formed to support the workpiece
170 can include additional horizontally extending strands to form
regions 174a and 174b of the brace structure 172 having greater
density of horizontally extending strands. In contrast, the curved
portion 172c with the higher radius of curvature is surrounded by a
region 174c of the brace structure 172 that has a lower density of
horizontally extending strands.
The greater density of the strands within the regions 174a, 174b
increases the ability of the brace structure 172 in areas proximate
the regions 174a, 174b to inhibit relative movement of the
workpiece 170 and the unfused powder. By inhibiting this relative
movement, the brace structure 172 enables fusing of the powder near
the regions 174a, 174b to achieve greater resolutions in comparison
to resolution achievable by fusing of the powder near the region
174c.
In the example as shown, the radius of curvature of the curved
portion 172c is sufficiently large such that the region 174c with
the lower density of strands is sufficient to achieve the
resolution necessary for the larger radius of curvature. To reduce
the amount of time to form the brace structure 172, particularly
within the region 174c, the controller can reduce the density of
the strands so that the brace structure 172 can be formed more
quickly. In this regard, to determine the density of the strands
within a region of the brace structure 172, the controller can
consider several factors, for example, the required resolution for
the workpiece near the region and the desired time to complete the
object. The controller can select the density of the strands within
the region such that each of the factors is fulfilled.
Furthermore, as shown in FIG. 3C, the brace structure 172 can form
several cells 176 that form a checkerboard pattern, e.g., in
contrast to the radial web pattern described and shown with respect
to FIGS. 3A and 3B. The individual strands of the brace structure
172, for example, intersect such that they are substantially
perpendicular (e.g., between 85 degrees and 95 degrees) relative to
one another. Within the regions 174a, 174b, the checkerboard
pattern of the brace structure 172 has a greater density of cells
176, e.g., there are a greater number of cells per unit area within
the regions 174a, 174b. Within the region 174c, the checkerboard
pattern of the brace structure 172 has a smaller density of cells
176, e.g., there are fewer cells per unit area within the region
174c.
In some implementations, each cell of the checkerboard pattern has
substantially equal side lengths such that each cell is
substantially square. In some examples, each cell is rectangular.
While the radial web pattern and the checkboard pattern for a level
of the brace structure have been described, in other examples, the
pattern formed within a level of the brace structure can be other
appropriate patterns, including a hexagonal pattern, a circular
pattern, or combinations of the patterns described herein. The
controller alternatively selects the pattern for a particular
region of the brace structure depending on the geometry of the
workpiece near that region.
Operations of the Additive Manufacturing Apparatus
The additive manufacturing apparatus, e.g., a controller of the
apparatus, performs operations and processes to build the
structures described herein to support the workpiece. Referring to
FIG. 1A, 1B, the controller 138 can operate the apparatus 100, and
in particular, the dispensing system 122 to control the dispensing
operations. The controller 138 can receive signals from, for
example, a user input on a user interface of the apparatus or
sensing signals from sensors of the apparatus 100. The user input
can CAD data indicative of the object to be formed. The controller
138 can use that CAD data to determine properties of the structures
formed during additive manufacturing processes. Based on the CAD
data, the controller 138 can generate instructions usable by each
of the systems operable with the controller 138, for example, to
dispense the powder, to fuse the powder, to move various systems of
the apparatus 100, and to sense properties of the systems, powder,
and/or the workpiece 142.
In an example process of forming an object, a controller (e.g., the
controller 138) controls systems of an additive manufacturing
apparatus to dispense (e.g., using the dispensing system 122) and
to fuse (e.g., using the energy source 124) powder on a build
platform (e.g., the build platform 104). FIGS. 4A to 4F depict
sequential operations 400A to 400F in which the controller uses the
additive manufacturing apparatus to perform these operations of
forming the object. Before beginning the operations 400A to 400F,
the controller of the apparatus can receive CAD data indicative of
the object to be formed. As is described herein, using the CAD
data, the controller can select properties of various structures
formed during the operations 400A to 400F. For example, the
controller can select a configuration of the brace structure to
support the object to be formed.
At operation 400A, as depicted in FIG. 4A, the controller controls
the dispensing system of the apparatus to dispense a group of one
or more layers 402 of powder particles on a build platform 404. The
apparatus can be, for example, the apparatus 100 described with
respect to FIG. 1A. The controller can be, for example, the
controller 138 of the apparatus 100 described with respect to FIG.
1A. The build platform 404 can be the build platform 104 of the
apparatus 100. When the apparatus dispenses the group of layers
402, the group of layers 402 can have a height that extends to a
top surface of side walls 405 of the apparatus.
While the dispensing system dispenses the group of layers 402, for
each layer within the group of layers 402, the controller
determines whether to operate the energy source to fuse portions of
the layer of the powder particles to form fused structures. Some of
the fused structures form a workpiece 406 that forms part of the
final object to be formed by the apparatus. In this regard, for
each layer within the group of layers 402, the controller operates
the energy source to fuse an object region such that the powder
within that area fuses to form part of the workpiece 406. Because
the geometry of the horizontal cross-section of the object can
change from layer to layer, the object region can vary from layer
to layer within the group of layers 402 to achieve these various
geometries.
Some of the fused structures form a brace structure 408 that
supports the workpiece 406 within the group of layers 402 of the
powder particles. The brace structure 408 serves a similar function
as, for example, the brace structures 144, 156, 164, 172 described
herein. For each layer within the group of layers 402, the
controller determines whether to operate the energy source to fuse
a brace region such that the powder within that area fuses to form
part of the brace structure 408.
The brace region can differ between the layers so that the brace
structure 408 formed includes the various types of structural
strands described with respect to the brace structures 144, 156,
164, 172. For example, as shown in FIG. 4A, the brace region within
the layers forming a horizontal level 410 of the brace structure
408 differs from the brace region within the layers forming
vertically extending portions 412.
To form the horizontal level 410, the brace region can include an
object perimeter region that forms an inner perimeter brace spaced
apart from and surrounding a perimeter of the object region within
the layer or layers forming the horizontal level 410. The inner
perimeter brace is similar to, for example, the inner perimeter
strand 148a described with respect to FIG. 2. To form the inner
perimeter brace, the controller optionally determines an offset
distance based on a perimeter of the object region within the layer
of powder forming the horizontal level. For example, the offset
distance can be between 1 and 10 voxels.
In some implementations, the controller determines the offset
distance between the inner perimeter brace and the perimeter of the
object region within the layers forming the horizontal level based
on the perimeter of object regions in layers outside of the layers
forming the horizontal level 410. For example, the controller can
select the offset distance such that the perimeter brace within the
layers forming the horizontal level 410 encompasses a horizontal
projection of the object within the layers forming the horizontal
level 410. In this regard, the perimeter brace can encompass the
perimeter of the object region for each of the successive layers
dispensed or to be dispensed.
The brace region can also include regions to form the radially
extending strands that radiate from near the workpiece 406, e.g.,
from the inner perimeter brace, toward the outer perimeter of the
build platform 404. These radially extending strands correspond to,
for example, the strands 146 of the brace structure 144.
In some implementations, the controller operates the energy source
to fuse connecting strands, e.g., similar to the connecting strands
148a, 148b, 148c of the brace structure 144. The connecting strands
and the radially extending strands together can form the horizontal
level 410 of the brace structure 408, and thus form a mesh-like
structure. The brace region fused by the energy source can
therefore be a mesh region.
Alternatively or additionally, the controller controls the energy
source to fuse some portions of the group of layers 402 to form
vertically extending portions 412 of the brace structure 408. The
vertically extending portions 412, if present, correspond to the
vertically extending strands 144d described with respect to the
brace structure 144.
Optionally, as described herein, one or more of the bottommost
layers is left unfused so that neither the workpiece 406 nor the
brace structure 408 contact the build platform 404. In some cases,
the workpiece 406 contacts the build platform 404 while the brace
structure 408 does not contact the build platform 404.
At operation 400B depicted in FIG. 4B, the controller continues
controlling the dispensing system to dispense additional groups of
layers 414, 416. While the groups of layers 414, 416 are being
dispensed, the controller controls the energy source to selectively
fuse portions of the layers to form the workpiece 406 as well as
the brace structure 408.
Optionally, the controller determines whether additional levels
(e.g., similar to the horizontal level 410) of the brace structure
408 are formed as the groups of layers 414, 416 are dispensed. The
controller determines that additional levels of the brace structure
408 are fused based on, for example, the geometry of the workpiece
406. As shown in FIG. 4B, the brace structure 408 does not include
horizontal levels within the groups of layers 414, 416. The
controller may determine to not control the energy source to fuse
horizontal levels within the groups of layers 414, 416 because the
horizontal cross-sectional geometry of the workpiece 406 does not
substantially change within these layers.
In some examples, the controller determines the geometry of the
workpiece 406 using the CAD data and can compute geometric overlap
between two or more portions of the object, particularly between
two or more portions of the object that would be positioned in
different groups of layers during the build process. If the
geometric overlap between two portions is below a threshold
overlap, the controller can generate instructions to control the
dispensing system and the energy source so as to form horizontal
levels of the brace structure in the layers containing the
geometric transition between the two layers. The geometric overlap
can correspond to a percent overlap between a parallel projection
of one of the portions on the top surface of the build platform 404
and a parallel projection of the other portion on the top surface
of the build platform 404. The threshold overlap can be, for
example, a threshold percent overlap between 50% and 90%.
For example, as shown at operation 400C depicted in FIG. 4C, the
workpiece 406 includes a stepped portion 418 in its geometry. Thus,
within the groups of layers 420, the controller selects a brace
region based on the geometry of the workpiece 406 within the group
of layers 420. As shown in FIG. 4C, the horizontal cross-section of
the workpiece 406 within the group of layers 420 has a greater
width than the horizontal cross-section of the workpiece 406 within
the groups of layers 402, 414, 416. In this regard, the brace
structure 408, particularly an inner perimeter brace of a
horizontal level 422 formed within the group of layers 420 has a
correspondingly greater width as compared to the width of the inner
perimeter brace of the horizontal level 410.
While described as a stepped portion 418, other types of geometries
of the workpiece 406 can serve as a basis for the controller to
build a horizontal level in a particular group of layers. For
example, the controller can build a horizontal level within a
gradual geometric transition of the workpiece from one
cross-sectional area to another cross-sectional area.
The vertically extending portions 412 of the brace structure 408,
if present, connect the horizontal level 410 to the horizontal
level 422 to inhibit relative movement between the horizontal level
410 and the horizontal level 422. In some cases, to support the
vertically extending portions 412, the controller can operate the
energy source to form horizontal levels within groups of layers
even though the geometry of the workpiece 406 does not change
substantially within those groups of layer. For example, horizontal
levels along the length of the vertically extending portions 412
can inhibit buckling along the length of the vertically extending
portions 412.
At operation 400D depicted in FIG. 4D, an additional group of
layers 424 is dispensed above the underlying groups of layers. As
the geometry of the horizontal cross-section of the workpiece 406
in the group of layers 424 does not substantially change relative
to the geometry of the horizontal cross-section of the workpiece in
the group of layers 420, the controller controls the energy source
to continue forming the vertically extending portions 412 but does
not control the energy source to fuse horizontal levels within the
group of layers 424.
At operation 400E as depicted in FIG. 4E, the workpiece 406
includes another stepped portion 426. The controller operates the
dispensing system to continue dispensing yet another group of
layers 425. The controller, meanwhile, also operates the energy
source to continue forming the vertically extending portions 412
and, because of the stepped portion 426, to form yet another
horizontal level 428 to support the workpiece 406. The brace
structure 408 within the horizontal level 428 has a geometry that
matches the geometry of the workpiece 406 within the group of
layers 425.
At operation 400F depicted in FIG. 4F, the controller has completed
the process of dispensing and fusing the powder to form the object,
e.g., the workpiece 406. The controller operates a robot arm 430,
if present, to remove the brace structure 408 from the workpiece
406. After removing the brace structure 408 from the workpiece 406,
the robot arm 430 can remove the workpiece 406 from the build
platform 404. In some examples, a human operator performs one or
more of the operations of removing the brace structure 408 from the
workpiece 406, removing the brace structure 408 from the build
platform 404, and removing the workpiece 406 from the build
platform 404.
In some examples, the robot arm 430 removes the workpiece 406 with
the brace structure 408 from the build platform 404. The brace
structure 408 can be formed in such a manner that each of the
horizontal levels 410, 422, 428 can be moved along a longitudinal
axis of the workpiece 406 (e.g., a vertical axis as shown in FIGS.
4A to 4F) and be removed from an upper and/or lower end of the
workpiece 406. The horizontal levels 410, 422, 428 thus each has an
inner perimeter brace that enables the horizontal levels 410, 422,
428 to be removed from the workpiece 406 in this manner. In one
example, the controller determines the offset distance for each of
the inner perimeter braces for the horizontal levels 410, 422, 428
based on the perimeter of the object region of the workpiece 406 in
the group of layers corresponding to the position of the horizontal
levels 410, 422, 428.
The controller selects the offset distance such that the perimeter
of the object perimeter region forming the inner perimeter braces,
as projected on the top surface of build platform, contains at
least one of (i) the perimeter of the object region of each of the
layers of the workpiece 406 below the horizontal levels 410, 422,
428, as also projected on the top surface of the build platform 404
and (ii) the perimeter of the object region of the workpiece 406 of
each of the layers above the horizontal levels 410, 422, 428, as
projected on the top surface of the build platform 404. If the
perimeter of the inner perimeter brace for a horizontal level
contains the projected perimeter of the object regions below the
horizontal level, the horizontal level would be removable from the
lower end of the workpiece 406. If the perimeter of the inner
perimeter brace for the horizontal level contains the projected
perimeter of the object regions above the horizontal level, the
horizontal level would be removable from the upper end of the
workpiece 406.
In some cases, some of the horizontal levels are removable from the
upper end of the workpiece 406 while other horizontal levels are
removable from the lower end of the workpiece 406. The horizontal
levels removable from the upper end of the workpiece 406 can be
connected to one another by a set of vertically extending portions,
and the horizontal levels removable from the lower end of the
workpiece 406 can be connected to one another by another set of
vertically extending portions. The horizontal levels removable from
the upper end are not connected to the horizontal levels removable
from the lower end, e.g., they are not connected by vertically
extending portions. With this configuration of the brace structure,
the horizontal levels removable from the upper end with its
corresponding set of vertically extending portions form a first
brace structure, and the horizontal levels from the lower end with
its corresponding set of vertically extending portions form a
second brace structure. The first brace structure is removed by the
robot arm 430 by moving the first brace structure in a first
direction, e.g., an upward direction, relative to the workpiece
406. The second brace structure is removed by the robot arm 430 by
moving the second brace structure in a second direction, e.g., a
downward direction, relative to the workpiece 406.
The controller operates the robot arm 430 to manipulate the brace
structure 408 while the brace structure 408 is contained within the
build platform 104. In some examples, the controller operates the
robot arm 430 to break the brace structure 408 while the brace
structure 408 is contained within the build platform 104. The robot
arm 430 breaks the brace structure 408 along the vertically
extending portions 412 by, for example, twisting the brace
structure 408. The torsion from the twisting can cause the
vertically extending portions 412 to rupture, and the robot arm 430
can proceed to remove pieces of the brace structure 408 from the
workpiece 406.
If the brace structure 408 includes keyed portions, e.g., the keyed
portions 168, the robot arm 430 optionally includes an end effector
having a corresponding lock portion that engages with the keyed
portions 168. The lock portion has a geometry that matches the
geometry of the keyed portions 168 such that the robot arm 430 can
grasp the keyed portions 168. The robot arm 430 can include a lock
portion for each of the keyed portions present on the brace
structure 408. If the keyed portions 168 are present on the brace
structure 408, the controller removes the brace structure 408 from
the workpiece 406 by controlling the end effector of the robot arm
430 such that the lock portion engages with the keyed portion 168.
In some examples, the controller causes the lock portion to engage
the keyed portion 168 by rotating the robot arm 430 about a
vertical axis. The rotation of the robot arm 430 thereby causes the
lock portion to rotate into engagement with the keyed portion 168.
The lock portion of the end effector engaged with the keyed portion
168 enables the robot arm 430 to be coupled to the brace structure
408 such that vertical displacement of the robot arm 430 results in
vertical displacement of the brace structure 408.
While the operations 400A to 400F depicted in FIGS. 4A to 4F show a
single brace structure 408 with each of the horizontal levels
connected to one another by vertically extending portions 412, in
some examples, a workpiece can be supported by multiple brace
structures. As shown in FIG. 5, a workpiece 500 is supported by
multiple separated brace structures 502, 504, 506. Each of the
brace structures 502, 504, 506 includes only strands that would
form horizontal levels as described herein. In this regard, the
brace structures 502, 504, 506 do not include a vertically
extending portions.
In some implementations, as shown in FIG. 6, a workpiece 600 is
supported by brace structures 602 that are evenly spaced apart in a
vertical direction. A brace structure 602 can be formed in each of
the group of layers dispensed on the build platform.
Controllers and computing devices can implement these operations
and other processes and operations described herein. As described
above, the controller 138 of the apparatus 100 can include one or
more processing devices connected to the various components of the
apparatus 100, e.g., actuators, valves, and voltage sources, to
generate control signals for those components. The controller can
coordinate the operation and cause the apparatus 100 to carry out
the various functional operations or sequence of steps described
above. The controller can control the movement and operations of
the systems of the printhead 102. The controller 138, for example,
controls the location of feed material, including the first and
second powder particles. The controller 138 also controls the
intensity of the energy source based on the number of layers in a
group of layers to be fused at once. The controller 138 also
controls the location where energy is added by, for example, moving
the energy source or the printhead.
The controller 138 and other computing devices part of systems
described herein can be implemented in digital electronic
circuitry, or in computer software, firmware, or hardware. For
example, the controller can include a processor to execute a
computer program as stored in a computer program product, e.g., in
a non-transitory machine readable storage medium. Such a computer
program (also known as a program, software, software application,
or code) can be written in any form of programming language,
including compiled or interpreted languages, and it can be deployed
in any form, including as a standalone program or as a module,
component, subroutine, or other unit suitable for use in a
computing environment.
The controller 138 and other computing devices part of systems
described can include non-transitory computer readable medium to
store a data object, e.g., a computer aided design (CAD)-compatible
file that identifies the pattern in which the feed material should
be deposited for each layer. For example, the data object could be
a STL-formatted file, a 3D Manufacturing Format (3MF) file, or an
Additive Manufacturing File Format (AMF) file. For example, the
controller could receive the data object from a remote computer. A
processor in the controller 138, e.g., as controlled by firmware or
software, can interpret the data object received from the computer
to generate the set of signals necessary to control the components
of the apparatus 100 to fuse the specified pattern for each
layer.
While this document contains many specific implementation details,
these should not be construed as limitations on the scope of any
inventions or of what may be claimed, but rather as descriptions of
features specific to particular embodiments of particular
inventions. Certain features that are described in this document in
the context of separate embodiments can also be implemented in
combination in a single embodiment. Conversely, various features
that are described in the context of a single embodiment can also
be implemented in multiple embodiments separately or in any
suitable subcombination. Moreover, although features may be
described above as acting in certain combinations and even
initially claimed as such, one or more features from a claimed
combination can in some cases be excised from the combination, and
the claimed combination may be directed to a subcombination or
variation of a subcombination.
The printhead of FIG. 1A includes several systems that enable the
apparatus 100 to build objects. In some cases, instead of a
printhead, an AM apparatus includes independently operated systems,
including independently operated energy sources, dispensers, and
sensors. Each of these systems can be independently moved and may
or may not be part of a modular printhead. In some examples, the
printhead includes only the dispensers, and the apparatus include
separate energy sources to perform the fusing operations. The
printhead in these examples would therefore cooperate with the
controller to perform the dispensing operations.
While the operations are described to include a single size of
powder particles, in some implementations, these operations can be
implemented with multiple different sizes of powder particles.
While some implementations of the AM apparatus described herein
include two types of particles (e.g., the first and the second
powder particles), in some cases, additional types of particles can
be used. As described above, the first powder particles have a
smaller size than the second powder particles. In some
implementations, prior to dispensing the second powder particles to
form a layer, the apparatus dispenses third powder particles onto
the platen or underlying previously dispensed layer. This third
powder particles can provide a thin layer onto which the first
powder particles are dispensed. The third powder particles having a
mean diameter that is at least two times smaller than the first
mean diameter. This permits the second powder particles to settle
into the layer of third particle particles. This technique can
increase the density of the object at the bottom of the layer of
second powder particles, e.g., if the first powder particles cannot
infiltrate to the bottom of the layer of second powder
particles.
The processing conditions for additive manufacturing of metals and
ceramics are significantly different than those for plastics. For
example, in general, metals and ceramics require significantly
higher processing temperatures. Thus 3D printing techniques for
plastic may not be applicable to metal or ceramic processing and
equipment may not be equivalent. However, some techniques described
here could be applicable to polymer powders, e.g. nylon, ABS,
polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and
polystyrene.
A number of implementations have been described. Nevertheless, it
will be understood that various modifications may be made. For
example, Multiple disconnected brace structures can be formed. Each
of the brace structure includes horizontal levels, vertically
extending portions, or combinations thereof The horizontal levels
can have strands of varying thickness. The strands closer to the
workpiece can have greater thickness to provide greater support for
the workpiece, thus decreasing the relative movement between the
workpiece and the horizontal levels. In some cases, the vertically
extending portions have strands of varying thickness. Vertically
extending portions of the brace structure can include diagonal
strands that extend both vertically and horizontally. The
combination of the diagonal strands, the vertical strands, and the
horizontal strands can form a truss-like structure that supports
the workpiece. The patterns described herein, including the
checkerboard pattern and the radial web pattern, can extend both
horizontally and vertically. The controller can determine the
thickness of the strands based on the structural configuration of
the brace structure. For example, for a brace structure with a
greater density of strands, the brace structure can include thinner
strands and rely on structural configuration to provide the support
for the workpiece. In contrast, for a brace structure with a
smaller density of strands, the strands may be thicker to provide
the support for the workpiece. The resolution for the brace
structure can be less than the resolution of the workpiece to
decrease the duration of time or the expenditure of energy used to
form the brace structure. If the apparatus dispenses two or more
types of powder, the brace structure can be formed from one type of
powder, e.g., the larger powder, and the workpiece can be formed
from another type of powder, e.g., the smaller powder. In addition
to or as an alternative to being removable from an upper end and a
lower end of the workpiece, the brace structure can be removable
from a side of the workpiece. The vertically extending strands can
be formed such that the workpiece is able to pass through openings
formed between the vertically extending strands. The vertically
extending strands can form patterns while the horizontally
extending strands can connect the vertically extending strands. For
example, a set of vertically extending strands can form a radial
web pattern or a checkerboard pattern similar to a horizontal level
described herein. Another set can also form a radial web pattern or
a checkerboard pattern. The horizontally extending strands can
connect the two sets of vertically extending strands. Accordingly,
other implementations are within the scope of the claims.
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